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Table 4 Risk of breast cancer subgroups defined by type and receptor status in relation to total duration of breastfeeding

From: Breastfeeding in relation to risk of different breast cancer characteristics

Tumour subgroup Breastfeeding total in months Number of cases Incidence/100000 RR RR*
Ductal#      
  <4.0 59 199 1.00 1.00
  ≥4.0 - <8.0 74 197 0.99 (0.70 - 1.39) 0.99 (0.70 - 1.41)
  ≥8.0 - <13.0 74 206 1.03 (0.73 - 1.45) 1.04 (0.72 - 1.51)
  ≥13.0 79 224 1.12 (0.80 - 1.58) 1.20 (0.81 - 1.78)
  Missing 12 199 --- ---
  Total 298 207 p-trend:0.45 p-trend:0.26
Lobular      
  <4.0 15 51 1.00 1.00
  ≥4.0 - <8.0 21 56 1.11 (0.57 - 2.15) 0.95 (0.48 - 1.88)
  ≥8.0 - <13.0 23 64 1.27 (0.66 - 2.43) 1.02 (0.51 - 2.04)
  ≥13.0 14 40 0.79 (0.38 - 1.63) 0.65 (0.29 - 1.45)
  Missing 9 150 --- ---
  Total 82 57 p-trend:0.63 p-trend:0.44
Tubular      
  <4.0 4 13 1.00 1.00
  ≥4.0 - <8.0 10 27 1.97 (0.62 - 6.29) 2.09 (0.64 - 6.89)
  ≥8.0 - <13.0 7 20 1.43 (0.42 - 4.89) 1.59 (0.43 - 5.91)
  ≥13.0 6 17 1.26 (0.36 - 4.47) 1.56 (0.37 - 6.70)
  Missing 2 33 --- ---
  Total 29 20 p-trend:.1.00 p-trend:0.75
ERα neg ≤10%#      
  <4.0 9 30 1.00 1.00
  ≥4.0 - <8.0 12 32 1.05 (0.44 - 2.50) 1.16 (0.48 - 2.83)
  ≥8.0 - <13.0 13 36 1.18 (0.50 - 2.75) 1.38 (0.55 - 3.47)
  ≥13.0 15 43 1.40 (0.61 - 3.19) 1.61 (0.60 - 4.35)
  Missing 1 17 --- ---
  Total 50 35 p-trend:0.38 p-trend:0.30
ERα pos >10%      
  <4.0 61 206 1.00 1.00
  ≥4.0 - <8.0 85 227 1.10 (0.79 - 1.53) 1.06 (0.75 - 1.48)
  ≥8.0 - <13.0 88 245 1.19 (0.86 - 1.64) 1.13 (0.79 - 1.60)
  ≥13.0 80 227 1.10 (0.79 - 1.54) 1.09 (0.75 - 1.61)
  Missing 20 332 --- ---
  Total 334 232 p-trend:0.52 p-trend:0.47
ERβ neg ≤10%#      
  <4.0 29 98 1.00 1.00
  ≥4.0 - <8.0 38 101 1.04 (0.64 - 1.68) 1.04 (0.63 - 1.70)
  ≥8.0 - <13.0 44 123 1.26 (0.79 - 2.01) 1.26 (0.76 - 2.09)
  ≥13.0 40 114 1.16 (0.72 - 1.87) 1.20 (0.69 - 2.09)
  Missing 9 150 --- ---
  Total 160 111 p-trend:0.40 p-trend:0.32
ERβ pos >10%      
  <4.0 33 111 1.00 1.00
  ≥4.0 - <8.0 41 109 0.98 (0.62 - 1.54) 0.95 (0.59 - 1.53)
  ≥8.0 - <13.0 40 111 0.98 (0.62 - 1.55) 0.93 (0.57 - 1.53)
  ≥13.0 33 94 0.84 (0.52 - 1.35) 0.80 (0.46 - 1.40)
  Missing 9 150 --- ---
  Total 156 108 p-trend:0.48 p-trend:0.62
PgR neg ≤10%#      
  <4.0 42 142 1.00 1.00
  ≥4.0 - <8.0 49 131 0.92 (0.61 - 1.39) 0.91 (0.59 - 1.38)
  ≥8.0 - <13.0 50 139 0.98 (0.65 - 1.48) 0.96 (0.62 - 1.49)
  ≥13.0 49 139 0.98 (0.65 - 1.48) 1.01 (0.63 - 1.63)
  Missing 9 150 --- ---
  Total 199 138 p-trend:0.98 p-trend:0.90
PgR pos >10%      
  <4.0 28 94 1.00 1.00
  ≥4.0 - <8.0 40 107 1.12 (0.69 - 1.82) 1.13 (0.69 - 1.86)
  ≥8.0 - <13.0 43 120 1.25 (0.78 - 2.02) 1.30 (0.78 - 2.16)
  ≥13.0 38 108 1.14 (0.70 - 1.85) 1.24 (0.70 - 2.17)
  Missing 10 166 --- ---
  Total 159 110 p-trend:0.55 p-trend:0.29
  1. *Adjusted for age at baseline (continuous), education, socioeconomic status, marital status, age at menarche, age at first birth, parity, oophorectomy, age at menopause, oral contraceptive use, hormone replacement therapy use, bmi, alcohol consumption, smoking and height.
  2. #Reference group in heterogeneity analyses.